One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,3,5)(4,6,8,7)(9,10,17,24)(11,25,31,36)(12,18,32,21)(13,33,14,20)(15,23,16,22)(19,26,38,28)(27,37,40,34)(29,35,30,39)(2,5)(6,7)(10,18)(11,26)(12,14)(13,32)(15,16)(19,34)(20,22)(21,24)(23,33)(25,36)(27,30)(28,31)(29,40)(37,38) involution — undirected(2,6)(4,8)(5,7)(9,11,13,26,15,29,12,27,17,31,14,28,16,30,32,40)(10,19,21,36,22,37,20,35,24,38,18,25,23,34,33,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.